Method of sealing a fastener
A method for sealing a fastener employs a mold which provided with an inlet port for molding material. The mold is then positioned over a fastener and the mold is sealed against a structure. A moisture cured polyurethane reactive adhesive (MCRPA) as a molding material is then heated and injected into the mold. Upon solidification of the MCRPA, the mold is then removed to expose the MCRPA to atmospheric moisture and cured to leave an in-situ molded cap formed over the fastener and sealed to the structure.
1. A method for sealing a fastener comprising the steps of:
providing a mold having an inlet port for molding material;
positioning the mold over a fastener;
sealing the mold against a structure;
heating a moisture cured polyurethane reactive adhesive (MCRPA) to above melting temperature;
injecting the MCRPA as the molding material into the mold to fill the mold with any overflow routed through an overflow port;
solidifying the MCRPA in a molded cap shape; and,
removing the mold exposing the MCRPA to atmospheric moisture;
moisture curing the MCRPA to leave an in-situ formed molded cap over the fastener and adhered to the structure.
2. The method as defined in claim 1 wherein the MCRPA adheres to the fastener and the structure.
3. The method as defined in claim 1 wherein the mold provides a sealing circumference on a surface of the structure around the fastener, said molded cap adhered and sealed to the surface within the sealing circumference.
4. The method as defined in claim 1 wherein the MCPRA has a melting temperature of 250° F. or less.
5. The method as defined in claim 1 wherein the mold is formed from stainless steel.
6. The method as defined in claim 5 further comprising spraying a release agent into a cavity in the mold prior to positioning the mold.
7. The method as defined in claim 1 further comprising applying a surface treatment to the surface prior to positioning the mold.
8. The method as defined in claim 7 wherein applying a surface treatment to the surface prior to positioning the mold comprises a solvent wipe.
9. The method as defined in claim 1 wherein the MCRPA has application viscosity in the range of 7,000 to 16,000 cps and a molten density of 8.7 to 9.1 lbs/gal.
10. The method as defined in claim 1 wherein the MCRPA has cured modulus of elasticity between 2,850 psi and 5,600 psi with tensile strength of between 2,750 psi and 3,900 psi and Shore D hardness between 35 and 50.
11. The method as defined in claim 1 wherein the steps of heating and injecting molding material are performed with a handheld gun.
12. The method as defined in claim 1 wherein the steps of applying the mold and sealing the mold are automated.
13. The method as defined in claim 1 wherein the fastener comprises an array of fasteners and the step of positioning the mold comprises positioning the mold over the array of fasteners.